Contingent Liabilities and Commitments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Oct. 31, 2013	Jul. 31, 2013	Oct. 31, 2013 Standby Repurchase Obligations On Dealer Inventory Financing
Loss Contingencies [Line Items]
Standby repurchase obligations amount			$ 1,066,044
Term of commitments			Up to eighteen months
Repurchase and guarantee reserve balances	3,855	3,778
Chassis delivered to customers in days	90 days
Chassis consigned inventory	0
Additional chassis provided by customers	$ 206